The thing is that they've had this issue for several months now, so regardless of which side would've been at fault (if not both), Kiara would've likely had to have known she would not be able to have her video shown.
For all we know, maybe she sent the video in as just a personal thing for Pomu alone, with some note saying "btw, don't actually show this, you know, the usual stuff". Alternatively, mega rrat, she didn't send any video in, and Pomu just made a joke. We know absolutely nothing about what the situation is, so making rrats about it is kind of asinine. Tribalfags on either side of the fence will just pick out what they wanna hear either way, whether "evil controlling Holo bad", or "petty sore loser Niji bad".
Either way, most people can probably agree that they should just get the fucking permission already, and anyone blocking it is a giant faggot. Don't get me wrong, "absolute unity" fags who go "they should all just collab, I wanna see Petra with Gura! So what if they might have zero chemistry and be extremely fucking awkward together, they're both water-themed!" don't know what they're talking about. When two Vtubers wanna collab that badly though, and they have this much seemingly connecting them, not being able to actually collab is ridiculous.
